A balance beam scale is very different from the electronic scale you may have in your bathroom. Scales are measuring devices. That is true for both instruments, but when you step on an electronic scale, you are determining how much your body weighs. Balance beam scales do not measure weight, instead they value mass. The formats of these scales differ greatly in theory, purpose and style.
A balance scale compares the mass of two objects. One is a constant, an object where the exact mass is known. The two items sit on opposite sides of a long beam. The beam is precariously situated on a pivot arm, or fulcrum. When the two objects balance at the exact same level, they have equilibrium, or the same mass.
Electronic scales use electrical resistance to determine the weight of an object. The website Quick Supply describes the process as weight shifting the location of a load cell to change the electronic resistance. Load cells carry an electrical change. When an object, such as a human body, sits on top of the load cell, the weight bends it downward to shift the resistance. The degree of the shift goes through a microchip to calculate the weight of the object. Balance beam scales work on the theory of mass, while electronic scales measure weight.
Mass Vs. Weight
The University of California Department of Physics and Astronomy explains that weight is the force of the gravity puts on the mass of an object. Weight measurements calculate how much gravity it takes to hold an object to the earth. Mass, on the other hand, is about solidity. Mass is a quantifiable measurement of the amount of substance it takes to make an object solid. Balance scales measure mass. An electronic scale measures weight.
Manual Vs. Computerized
Another significant difference in these two measuring device is technology. Electronic scales use a computerized component to determine the weight. The human eye cannot see the bend in electronic resistance that reads the weight of an object. Electronic scales require the use of a microchip to make a calculation. Conversely, balance beam scales are very much a manual process. You physically place two objects together and compare the mass. Your eye makes the determination that the two objects reach equilibrium.
Both devices have similar usage. However, balance scales are primary for precision. They are the choice for medical purposes, such as doctor's offices and laboratories. Electronic scales can also be found in some medical practices and are popular for home use. When you need a fast weight and exact precision is not a requirement, an electronic scale will suffice.